// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Shared Transport Line discipline driver Core
 *      This hooks up ST KIM driver and ST LL driver
 *  Copyright (C) 2009-2010 Texas Instruments
 *  Author: Pavan Savoy <pavan_savoy@ti.com>
 */

#define pr_fmt(fmt)     "(stc): " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/tty.h>

#include <linux/seq_file.h>
#include <linux/skbuff.h>

#include <linux/ti_wilink_st.h>

extern void st_kim_recv(void *, const unsigned char *, long);
void st_int_recv(void *, const unsigned char *, long);
/* function pointer pointing to either,
 * st_kim_recv during registration to receive fw download responses
 * st_int_recv after registration to receive proto stack responses
 */
static void (*st_recv) (void *, const unsigned char *, long);

/********************************************************************/
static void add_channel_to_table(struct st_data_s *st_gdata,
                struct st_proto_s *new_proto)
{
        pr_info("%s: id %d\n", __func__, new_proto->chnl_id);
        /* list now has the channel id as index itself */
        st_gdata->list[new_proto->chnl_id] = new_proto;
        st_gdata->is_registered[new_proto->chnl_id] = true;
}

static void remove_channel_from_table(struct st_data_s *st_gdata,
                struct st_proto_s *proto)
{
        pr_info("%s: id %d\n", __func__, proto->chnl_id);
/*      st_gdata->list[proto->chnl_id] = NULL; */
        st_gdata->is_registered[proto->chnl_id] = false;
}

/*
 * called from KIM during firmware download.
 *
 * This is a wrapper function to tty->ops->write_room.
 * It returns number of free space available in
 * uart tx buffer.
 */
int st_get_uart_wr_room(struct st_data_s *st_gdata)
{
        struct tty_struct *tty;
        if (unlikely(st_gdata == NULL || st_gdata->tty == NULL)) {
                pr_err("tty unavailable to perform write");
                return -1;
        }
        tty = st_gdata->tty;
        return tty->ops->write_room(tty);
}

/* can be called in from
 * -- KIM (during fw download)
 * -- ST Core (during st_write)
 *
 *  This is the internal write function - a wrapper
 *  to tty->ops->write
 */
int st_int_write(struct st_data_s *st_gdata,
        const unsigned char *data, int count)
{
        struct tty_struct *tty;
        if (unlikely(st_gdata == NULL || st_gdata->tty == NULL)) {
                pr_err("tty unavailable to perform write");
                return -EINVAL;
        }
        tty = st_gdata->tty;
#ifdef VERBOSE
        print_hex_dump(KERN_DEBUG, "<out<", DUMP_PREFIX_NONE,
                16, 1, data, count, 0);
#endif
        return tty->ops->write(tty, data, count);

}

/*
 * push the skb received to relevant
 * protocol stacks
 */
static void st_send_frame(unsigned char chnl_id, struct st_data_s *st_gdata)
{
        pr_debug(" %s(prot:%d) ", __func__, chnl_id);

        if (unlikely
            (st_gdata == NULL || st_gdata->rx_skb == NULL
             || st_gdata->is_registered[chnl_id] == false)) {
                pr_err("chnl_id %d not registered, no data to send?",
                           chnl_id);
                kfree_skb(st_gdata->rx_skb);
                return;
        }
        /* this cannot fail
         * this shouldn't take long
         * - should be just skb_queue_tail for the
         *   protocol stack driver
         */
        if (likely(st_gdata->list[chnl_id]->recv != NULL)) {
                if (unlikely
                        (st_gdata->list[chnl_id]->recv
                        (st_gdata->list[chnl_id]->priv_data, st_gdata->rx_skb)
                             != 0)) {
                        pr_err(" proto stack %d's ->recv failed", chnl_id);
                        kfree_skb(st_gdata->rx_skb);
                        return;
                }
        } else {
                pr_err(" proto stack %d's ->recv null", chnl_id);
                kfree_skb(st_gdata->rx_skb);
        }
        return;
}

/**
 * st_reg_complete -
 * to call registration complete callbacks
 * of all protocol stack drivers
 * This function is being called with spin lock held, protocol drivers are
 * only expected to complete their waits and do nothing more than that.
 */
static void st_reg_complete(struct st_data_s *st_gdata, int err)
{
        unsigned char i = 0;
        pr_info(" %s ", __func__);
        for (i = 0; i < ST_MAX_CHANNELS; i++) {
                if (likely(st_gdata != NULL &&
                        st_gdata->is_registered[i] == true &&
                                st_gdata->list[i]->reg_complete_cb != NULL)) {
                        st_gdata->list[i]->reg_complete_cb
                                (st_gdata->list[i]->priv_data, err);
                        pr_info("protocol %d's cb sent %d\n", i, err);
                        if (err) { /* cleanup registered protocol */
                                st_gdata->is_registered[i] = false;
                                if (st_gdata->protos_registered)
                                        st_gdata->protos_registered--;
                        }
                }
        }
}

static inline int st_check_data_len(struct st_data_s *st_gdata,
        unsigned char chnl_id, int len)
{
        int room = skb_tailroom(st_gdata->rx_skb);

        pr_debug("len %d room %d", len, room);

        if (!len) {
                /* Received packet has only packet header and
                 * has zero length payload. So, ask ST CORE to
                 * forward the packet to protocol driver (BT/FM/GPS)
                 */
                st_send_frame(chnl_id, st_gdata);

        } else if (len > room) {
                /* Received packet's payload length is larger.
                 * We can't accommodate it in created skb.
                 */
                pr_err("Data length is too large len %d room %d", len,
                           room);
                kfree_skb(st_gdata->rx_skb);
        } else {
                /* Packet header has non-zero payload length and
                 * we have enough space in created skb. Lets read
                 * payload data */
                st_gdata->rx_state = ST_W4_DATA;
                st_gdata->rx_count = len;
                return len;
        }

        /* Change ST state to continue to process next
         * packet */
        st_gdata->rx_state = ST_W4_PACKET_TYPE;
        st_gdata->rx_skb = NULL;
        st_gdata->rx_count = 0;
        st_gdata->rx_chnl = 0;

        return 0;
}

/**
 * st_wakeup_ack - internal function for action when wake-up ack
 *      received
 */
static inline void st_wakeup_ack(struct st_data_s *st_gdata,
        unsigned char cmd)
{
        struct sk_buff *waiting_skb;
        unsigned long flags = 0;

        spin_lock_irqsave(&st_gdata->lock, flags);
        /* de-Q from waitQ and Q in txQ now that the
         * chip is awake
         */
        while ((waiting_skb = skb_dequeue(&st_gdata->tx_waitq)))
                skb_queue_tail(&st_gdata->txq, waiting_skb);

        /* state forwarded to ST LL */
        st_ll_sleep_state(st_gdata, (unsigned long)cmd);
        spin_unlock_irqrestore(&st_gdata->lock, flags);

        /* wake up to send the recently copied skbs from waitQ */
        st_tx_wakeup(st_gdata);
}

/**
 * st_int_recv - ST's internal receive function.
 *      Decodes received RAW data and forwards to corresponding
 *      client drivers (Bluetooth,FM,GPS..etc).
 *      This can receive various types of packets,
 *      HCI-Events, ACL, SCO, 4 types of HCI-LL PM packets
 *      CH-8 packets from FM, CH-9 packets from GPS cores.
 */
void st_int_recv(void *disc_data,
        const unsigned char *data, long count)
{
        char *ptr;
        struct st_proto_s *proto;
        unsigned short payload_len = 0;
        int len = 0;
        unsigned char type = 0;
        unsigned char *plen;
        struct st_data_s *st_gdata = (struct st_data_s *)disc_data;
        unsigned long flags;

        ptr = (char *)data;
        /* tty_receive sent null ? */
        if (unlikely(ptr == NULL) || (st_gdata == NULL)) {
                pr_err(" received null from TTY ");
                return;
        }

        pr_debug("count %ld rx_state %ld"
                   "rx_count %ld", count, st_gdata->rx_state,
                   st_gdata->rx_count);

        spin_lock_irqsave(&st_gdata->lock, flags);
        /* Decode received bytes here */
        while (count) {
                if (st_gdata->rx_count) {
                        len = min_t(unsigned int, st_gdata->rx_count, count);
                        skb_put_data(st_gdata->rx_skb, ptr, len);
                        st_gdata->rx_count -= len;
                        count -= len;
                        ptr += len;

                        if (st_gdata->rx_count)
                                continue;

                        /* Check ST RX state machine , where are we? */
                        switch (st_gdata->rx_state) {
                        /* Waiting for complete packet ? */
                        case ST_W4_DATA:
                                pr_debug("Complete pkt received");
                                /* Ask ST CORE to forward
                                 * the packet to protocol driver */
                                st_send_frame(st_gdata->rx_chnl, st_gdata);

                                st_gdata->rx_state = ST_W4_PACKET_TYPE;
                                st_gdata->rx_skb = NULL;
                                continue;
                        /* parse the header to know details */
                        case ST_W4_HEADER:
                                proto = st_gdata->list[st_gdata->rx_chnl];
                                plen =
                                &st_gdata->rx_skb->data
                                [proto->offset_len_in_hdr];
                                pr_debug("plen pointing to %x\n", *plen);
                                if (proto->len_size == 1)/* 1 byte len field */
                                        payload_len = *(unsigned char *)plen;
                                else if (proto->len_size == 2)
                                        payload_len =
                                        __le16_to_cpu(*(unsigned short *)plen);
                                else
                                        pr_info("%s: invalid length "
                                        "for id %d\n",
                                        __func__, proto->chnl_id);
                                st_check_data_len(st_gdata, proto->chnl_id,
                                                payload_len);
                                pr_debug("off %d, pay len %d\n",
                                        proto->offset_len_in_hdr, payload_len);
                                continue;
                        }       /* end of switch rx_state */
                }

                /* end of if rx_count */
                /* Check first byte of packet and identify module
                 * owner (BT/FM/GPS) */
                switch (*ptr) {
                case LL_SLEEP_IND:
                case LL_SLEEP_ACK:
                case LL_WAKE_UP_IND:
                        pr_debug("PM packet");
                        /* this takes appropriate action based on
                         * sleep state received --
                         */
                        st_ll_sleep_state(st_gdata, *ptr);
                        /* if WAKEUP_IND collides copy from waitq to txq
                         * and assume chip awake
                         */
                        spin_unlock_irqrestore(&st_gdata->lock, flags);
                        if (st_ll_getstate(st_gdata) == ST_LL_AWAKE)
                                st_wakeup_ack(st_gdata, LL_WAKE_UP_ACK);
                        spin_lock_irqsave(&st_gdata->lock, flags);

                        ptr++;
                        count--;
                        continue;
                case LL_WAKE_UP_ACK:
                        pr_debug("PM packet");

                        spin_unlock_irqrestore(&st_gdata->lock, flags);
                        /* wake up ack received */
                        st_wakeup_ack(st_gdata, *ptr);
                        spin_lock_irqsave(&st_gdata->lock, flags);

                        ptr++;
                        count--;
                        continue;
                        /* Unknow packet? */
                default:
                        type = *ptr;

                        /* Default case means non-HCILL packets,
                         * possibilities are packets for:
                         * (a) valid protocol -  Supported Protocols within
                         *     the ST_MAX_CHANNELS.
                         * (b) registered protocol - Checked by
                         *     "st_gdata->list[type] == NULL)" are supported
                         *     protocols only.
                         *  Rules out any invalid protocol and
                         *  unregistered protocols with channel ID < 16.
                         */

                        if ((type >= ST_MAX_CHANNELS) ||
                                        (st_gdata->list[type] == NULL)) {
                                pr_err("chip/interface misbehavior: "
                                                "dropping frame starting "
                                                "with 0x%02x\n", type);
                                goto done;
                        }

                        st_gdata->rx_skb = alloc_skb(
                                        st_gdata->list[type]->max_frame_size,
                                        GFP_ATOMIC);
                        if (st_gdata->rx_skb == NULL) {
                                pr_err("out of memory: dropping\n");
                                goto done;
                        }

                        skb_reserve(st_gdata->rx_skb,
                                        st_gdata->list[type]->reserve);
                        /* next 2 required for BT only */
                        st_gdata->rx_skb->cb[0] = type; /*pkt_type*/
                        st_gdata->rx_skb->cb[1] = 0; /*incoming*/
                        st_gdata->rx_chnl = *ptr;
                        st_gdata->rx_state = ST_W4_HEADER;
                        st_gdata->rx_count = st_gdata->list[type]->hdr_len;
                        pr_debug("rx_count %ld\n", st_gdata->rx_count);
                };
                ptr++;
                count--;
        }
done:
        spin_unlock_irqrestore(&st_gdata->lock, flags);
        pr_debug("done %s", __func__);
        return;
}

/**
 * st_int_dequeue - internal de-Q function.
 *      If the previous data set was not written
 *      completely, return that skb which has the pending data.
 *      In normal cases, return top of txq.
 */
static struct sk_buff *st_int_dequeue(struct st_data_s *st_gdata)
{
        struct sk_buff *returning_skb;

        pr_debug("%s", __func__);
        if (st_gdata->tx_skb != NULL) {
                returning_skb = st_gdata->tx_skb;
                st_gdata->tx_skb = NULL;
                return returning_skb;
        }
        return skb_dequeue(&st_gdata->txq);
}

/**
 * st_int_enqueue - internal Q-ing function.
 *      Will either Q the skb to txq or the tx_waitq
 *      depending on the ST LL state.
 *      If the chip is asleep, then Q it onto waitq and
 *      wakeup the chip.
 *      txq and waitq needs protection since the other contexts
 *      may be sending data, waking up chip.
 */
static void st_int_enqueue(struct st_data_s *st_gdata, struct sk_buff *skb)
{
        unsigned long flags = 0;

        pr_debug("%s", __func__);
        spin_lock_irqsave(&st_gdata->lock, flags);

        switch (st_ll_getstate(st_gdata)) {
        case ST_LL_AWAKE:
                pr_debug("ST LL is AWAKE, sending normally");
                skb_queue_tail(&st_gdata->txq, skb);
                break;
        case ST_LL_ASLEEP_TO_AWAKE:
                skb_queue_tail(&st_gdata->tx_waitq, skb);
                break;
        case ST_LL_AWAKE_TO_ASLEEP:
                pr_err("ST LL is illegal state(%ld),"
                           "purging received skb.", st_ll_getstate(st_gdata));
                kfree_skb(skb);
                break;
        case ST_LL_ASLEEP:
                skb_queue_tail(&st_gdata->tx_waitq, skb);
                st_ll_wakeup(st_gdata);
                break;
        default:
                pr_err("ST LL is illegal state(%ld),"
                           "purging received skb.", st_ll_getstate(st_gdata));
                kfree_skb(skb);
                break;
        }

        spin_unlock_irqrestore(&st_gdata->lock, flags);
        pr_debug("done %s", __func__);
        return;
}

/*
 * internal wakeup function
 * called from either
 * - TTY layer when write's finished
 * - st_write (in context of the protocol stack)
 */
static void work_fn_write_wakeup(struct work_struct *work)
{
        struct st_data_s *st_gdata = container_of(work, struct st_data_s,
                        work_write_wakeup);

        st_tx_wakeup((void *)st_gdata);
}
void st_tx_wakeup(struct st_data_s *st_data)
{
        struct sk_buff *skb;
        unsigned long flags;    /* for irq save flags */
        pr_debug("%s", __func__);
        /* check for sending & set flag sending here */
        if (test_and_set_bit(ST_TX_SENDING, &st_data->tx_state)) {
                pr_debug("ST already sending");
                /* keep sending */
                set_bit(ST_TX_WAKEUP, &st_data->tx_state);
                return;
                /* TX_WAKEUP will be checked in another
                 * context
                 */
        }
        do {                    /* come back if st_tx_wakeup is set */
                /* woke-up to write */
                clear_bit(ST_TX_WAKEUP, &st_data->tx_state);
                while ((skb = st_int_dequeue(st_data))) {
                        int len;
                        spin_lock_irqsave(&st_data->lock, flags);
                        /* enable wake-up from TTY */
                        set_bit(TTY_DO_WRITE_WAKEUP, &st_data->tty->flags);
                        len = st_int_write(st_data, skb->data, skb->len);
                        skb_pull(skb, len);
                        /* if skb->len = len as expected, skb->len=0 */
                        if (skb->len) {
                                /* would be the next skb to be sent */
                                st_data->tx_skb = skb;
                                spin_unlock_irqrestore(&st_data->lock, flags);
                                break;
                        }
                        kfree_skb(skb);
                        spin_unlock_irqrestore(&st_data->lock, flags);
                }
                /* if wake-up is set in another context- restart sending */
        } while (test_bit(ST_TX_WAKEUP, &st_data->tx_state));

        /* clear flag sending */
        clear_bit(ST_TX_SENDING, &st_data->tx_state);
}

/********************************************************************/
/* functions called from ST KIM
*/
void kim_st_list_protocols(struct st_data_s *st_gdata, void *buf)
{
        seq_printf(buf, "[%d]\nBT=%c\nFM=%c\nGPS=%c\n",
                        st_gdata->protos_registered,
                        st_gdata->is_registered[0x04] == true ? 'R' : 'U',
                        st_gdata->is_registered[0x08] == true ? 'R' : 'U',
                        st_gdata->is_registered[0x09] == true ? 'R' : 'U');
}

/********************************************************************/
/*
 * functions called from protocol stack drivers
 * to be EXPORT-ed
 */
long st_register(struct st_proto_s *new_proto)
{
        struct st_data_s        *st_gdata;
        long err = 0;
        unsigned long flags = 0;

        st_kim_ref(&st_gdata, 0);
        if (st_gdata == NULL || new_proto == NULL || new_proto->recv == NULL
            || new_proto->reg_complete_cb == NULL) {
                pr_err("gdata/new_proto/recv or reg_complete_cb not ready");
                return -EINVAL;
        }

        if (new_proto->chnl_id >= ST_MAX_CHANNELS) {
                pr_err("chnl_id %d not supported", new_proto->chnl_id);
                return -EPROTONOSUPPORT;
        }

        if (st_gdata->is_registered[new_proto->chnl_id] == true) {
                pr_err("chnl_id %d already registered", new_proto->chnl_id);
                return -EALREADY;
        }

        /* can be from process context only */
        spin_lock_irqsave(&st_gdata->lock, flags);

        if (test_bit(ST_REG_IN_PROGRESS, &st_gdata->st_state)) {
                pr_info(" ST_REG_IN_PROGRESS:%d ", new_proto->chnl_id);
                /* fw download in progress */

                add_channel_to_table(st_gdata, new_proto);
                st_gdata->protos_registered++;
                new_proto->write = st_write;

                set_bit(ST_REG_PENDING, &st_gdata->st_state);
                spin_unlock_irqrestore(&st_gdata->lock, flags);
                return -EINPROGRESS;
        } else if (st_gdata->protos_registered == ST_EMPTY) {
                pr_info(" chnl_id list empty :%d ", new_proto->chnl_id);
                set_bit(ST_REG_IN_PROGRESS, &st_gdata->st_state);
                st_recv = st_kim_recv;

                /* enable the ST LL - to set default chip state */
                st_ll_enable(st_gdata);

                /* release lock previously held - re-locked below */
                spin_unlock_irqrestore(&st_gdata->lock, flags);

                /* this may take a while to complete
                 * since it involves BT fw download
                 */
                err = st_kim_start(st_gdata->kim_data);
                if (err != 0) {
                        clear_bit(ST_REG_IN_PROGRESS, &st_gdata->st_state);
                        if ((st_gdata->protos_registered != ST_EMPTY) &&
                            (test_bit(ST_REG_PENDING, &st_gdata->st_state))) {
                                pr_err(" KIM failure complete callback ");
                                spin_lock_irqsave(&st_gdata->lock, flags);
                                st_reg_complete(st_gdata, err);
                                spin_unlock_irqrestore(&st_gdata->lock, flags);
                                clear_bit(ST_REG_PENDING, &st_gdata->st_state);
                        }
                        return -EINVAL;
                }

                spin_lock_irqsave(&st_gdata->lock, flags);

                clear_bit(ST_REG_IN_PROGRESS, &st_gdata->st_state);
                st_recv = st_int_recv;

                /* this is where all pending registration
                 * are signalled to be complete by calling callback functions
                 */
                if ((st_gdata->protos_registered != ST_EMPTY) &&
                    (test_bit(ST_REG_PENDING, &st_gdata->st_state))) {
                        pr_debug(" call reg complete callback ");
                        st_reg_complete(st_gdata, 0);
                }
                clear_bit(ST_REG_PENDING, &st_gdata->st_state);

                /* check for already registered once more,
                 * since the above check is old
                 */
                if (st_gdata->is_registered[new_proto->chnl_id] == true) {
                        pr_err(" proto %d already registered ",
                                   new_proto->chnl_id);
                        spin_unlock_irqrestore(&st_gdata->lock, flags);
                        return -EALREADY;
                }

                add_channel_to_table(st_gdata, new_proto);
                st_gdata->protos_registered++;
                new_proto->write = st_write;
                spin_unlock_irqrestore(&st_gdata->lock, flags);
                return err;
        }
        /* if fw is already downloaded & new stack registers protocol */
        else {
                add_channel_to_table(st_gdata, new_proto);
                st_gdata->protos_registered++;
                new_proto->write = st_write;

                /* lock already held before entering else */
                spin_unlock_irqrestore(&st_gdata->lock, flags);
                return err;
        }
}
EXPORT_SYMBOL_GPL(st_register);

/* to unregister a protocol -
 * to be called from protocol stack driver
 */
long st_unregister(struct st_proto_s *proto)
{
        long err = 0;
        unsigned long flags = 0;
        struct st_data_s        *st_gdata;

        pr_debug("%s: %d ", __func__, proto->chnl_id);

        st_kim_ref(&st_gdata, 0);
        if (!st_gdata || proto->chnl_id >= ST_MAX_CHANNELS) {
                pr_err(" chnl_id %d not supported", proto->chnl_id);
                return -EPROTONOSUPPORT;
        }

        spin_lock_irqsave(&st_gdata->lock, flags);

        if (st_gdata->is_registered[proto->chnl_id] == false) {
                pr_err(" chnl_id %d not registered", proto->chnl_id);
                spin_unlock_irqrestore(&st_gdata->lock, flags);
                return -EPROTONOSUPPORT;
        }

        if (st_gdata->protos_registered)
                st_gdata->protos_registered--;

        remove_channel_from_table(st_gdata, proto);
        spin_unlock_irqrestore(&st_gdata->lock, flags);

        if ((st_gdata->protos_registered == ST_EMPTY) &&
            (!test_bit(ST_REG_PENDING, &st_gdata->st_state))) {
                pr_info(" all chnl_ids unregistered ");

                /* stop traffic on tty */
                if (st_gdata->tty) {
                        tty_ldisc_flush(st_gdata->tty);
                        stop_tty(st_gdata->tty);
                }

                /* all chnl_ids now unregistered */
                st_kim_stop(st_gdata->kim_data);
                /* disable ST LL */
                st_ll_disable(st_gdata);
        }
        return err;
}

/*
 * called in protocol stack drivers
 * via the write function pointer
 */
long st_write(struct sk_buff *skb)
{
        struct st_data_s *st_gdata;
        long len;

        st_kim_ref(&st_gdata, 0);
        if (unlikely(skb == NULL || st_gdata == NULL
                || st_gdata->tty == NULL)) {
                pr_err("data/tty unavailable to perform write");
                return -EINVAL;
        }

        pr_debug("%d to be written", skb->len);
        len = skb->len;

        /* st_ll to decide where to enqueue the skb */
        st_int_enqueue(st_gdata, skb);
        /* wake up */
        st_tx_wakeup(st_gdata);

        /* return number of bytes written */
        return len;
}

/* for protocols making use of shared transport */
EXPORT_SYMBOL_GPL(st_unregister);

/********************************************************************/
/*
 * functions called from TTY layer
 */
static int st_tty_open(struct tty_struct *tty)
{
        int err = 0;
        struct st_data_s *st_gdata;
        pr_info("%s ", __func__);

        st_kim_ref(&st_gdata, 0);
        st_gdata->tty = tty;
        tty->disc_data = st_gdata;

        /* don't do an wakeup for now */
        clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

        /* mem already allocated
         */
        tty->receive_room = 65536;
        /* Flush any pending characters in the driver and discipline. */
        tty_ldisc_flush(tty);
        tty_driver_flush_buffer(tty);
        /*
         * signal to UIM via KIM that -
         * installation of N_TI_WL ldisc is complete
         */
        st_kim_complete(st_gdata->kim_data);
        pr_debug("done %s", __func__);
        return err;
}

static void st_tty_close(struct tty_struct *tty)
{
        unsigned char i = ST_MAX_CHANNELS;
        unsigned long flags = 0;
        struct  st_data_s *st_gdata = tty->disc_data;

        pr_info("%s ", __func__);

        /* TODO:
         * if a protocol has been registered & line discipline
         * un-installed for some reason - what should be done ?
         */
        spin_lock_irqsave(&st_gdata->lock, flags);
        for (i = ST_BT; i < ST_MAX_CHANNELS; i++) {
                if (st_gdata->is_registered[i] == true)
                        pr_err("%d not un-registered", i);
                st_gdata->list[i] = NULL;
                st_gdata->is_registered[i] = false;
        }
        st_gdata->protos_registered = 0;
        spin_unlock_irqrestore(&st_gdata->lock, flags);
        /*
         * signal to UIM via KIM that -
         * N_TI_WL ldisc is un-installed
         */
        st_kim_complete(st_gdata->kim_data);
        st_gdata->tty = NULL;
        /* Flush any pending characters in the driver and discipline. */
        tty_ldisc_flush(tty);
        tty_driver_flush_buffer(tty);

        spin_lock_irqsave(&st_gdata->lock, flags);
        /* empty out txq and tx_waitq */
        skb_queue_purge(&st_gdata->txq);
        skb_queue_purge(&st_gdata->tx_waitq);
        /* reset the TTY Rx states of ST */
        st_gdata->rx_count = 0;
        st_gdata->rx_state = ST_W4_PACKET_TYPE;
        kfree_skb(st_gdata->rx_skb);
        st_gdata->rx_skb = NULL;
        spin_unlock_irqrestore(&st_gdata->lock, flags);

        pr_debug("%s: done ", __func__);
}

static void st_tty_receive(struct tty_struct *tty, const unsigned char *data,
                           char *tty_flags, int count)
{
#ifdef VERBOSE
        print_hex_dump(KERN_DEBUG, ">in>", DUMP_PREFIX_NONE,
                16, 1, data, count, 0);
#endif

        /*
         * if fw download is in progress then route incoming data
         * to KIM for validation
         */
        st_recv(tty->disc_data, data, count);
        pr_debug("done %s", __func__);
}

/* wake-up function called in from the TTY layer
 * inside the internal wakeup function will be called
 */
static void st_tty_wakeup(struct tty_struct *tty)
{
        struct  st_data_s *st_gdata = tty->disc_data;
        pr_debug("%s ", __func__);
        /* don't do an wakeup for now */
        clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

        /*
         * schedule the internal wakeup instead of calling directly to
         * avoid lockup (port->lock needed in tty->ops->write is
         * already taken here
         */
        schedule_work(&st_gdata->work_write_wakeup);
}

static void st_tty_flush_buffer(struct tty_struct *tty)
{
        struct  st_data_s *st_gdata = tty->disc_data;
        pr_debug("%s ", __func__);

        kfree_skb(st_gdata->tx_skb);
        st_gdata->tx_skb = NULL;

        tty_driver_flush_buffer(tty);
        return;
}

static struct tty_ldisc_ops st_ldisc_ops = {
        .magic = TTY_LDISC_MAGIC,
        .name = "n_st",
        .open = st_tty_open,
        .close = st_tty_close,
        .receive_buf = st_tty_receive,
        .write_wakeup = st_tty_wakeup,
        .flush_buffer = st_tty_flush_buffer,
        .owner = THIS_MODULE
};

/********************************************************************/
int st_core_init(struct st_data_s **core_data)
{
        struct st_data_s *st_gdata;
        long err;

        err = tty_register_ldisc(N_TI_WL, &st_ldisc_ops);
        if (err) {
                pr_err("error registering %d line discipline %ld",
                           N_TI_WL, err);
                return err;
        }
        pr_debug("registered n_shared line discipline");

        st_gdata = kzalloc(sizeof(struct st_data_s), GFP_KERNEL);
        if (!st_gdata) {
                pr_err("memory allocation failed");
                err = tty_unregister_ldisc(N_TI_WL);
                if (err)
                        pr_err("unable to un-register ldisc %ld", err);
                err = -ENOMEM;
                return err;
        }

        /* Initialize ST TxQ and Tx waitQ queue head. All BT/FM/GPS module skb's
         * will be pushed in this queue for actual transmission.
         */
        skb_queue_head_init(&st_gdata->txq);
        skb_queue_head_init(&st_gdata->tx_waitq);

        /* Locking used in st_int_enqueue() to avoid multiple execution */
        spin_lock_init(&st_gdata->lock);

        err = st_ll_init(st_gdata);
        if (err) {
                pr_err("error during st_ll initialization(%ld)", err);
                kfree(st_gdata);
                err = tty_unregister_ldisc(N_TI_WL);
                if (err)
                        pr_err("unable to un-register ldisc");
                return err;
        }

        INIT_WORK(&st_gdata->work_write_wakeup, work_fn_write_wakeup);

        *core_data = st_gdata;
        return 0;
}

void st_core_exit(struct st_data_s *st_gdata)
{
        long err;
        /* internal module cleanup */
        err = st_ll_deinit(st_gdata);
        if (err)
                pr_err("error during deinit of ST LL %ld", err);

        if (st_gdata != NULL) {
                /* Free ST Tx Qs and skbs */
                skb_queue_purge(&st_gdata->txq);
                skb_queue_purge(&st_gdata->tx_waitq);
                kfree_skb(st_gdata->rx_skb);
                kfree_skb(st_gdata->tx_skb);
                /* TTY ldisc cleanup */
                err = tty_unregister_ldisc(N_TI_WL);
                if (err)
                        pr_err("unable to un-register ldisc %ld", err);
                /* free the global data pointer */
                kfree(st_gdata);
        }
}